US4808315A - Porous hollow fiber membrane and a method for the removal of a virus by using the same - Google Patents

Porous hollow fiber membrane and a method for the removal of a virus by using the same Download PDF

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US4808315A
US4808315A US07/082,730 US8273087A US4808315A US 4808315 A US4808315 A US 4808315A US 8273087 A US8273087 A US 8273087A US 4808315 A US4808315 A US 4808315A
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plane
wall
hollow fiber
porous
porosity
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Sei-ichi Manabe
Masuo Satani
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Asahi Kasei Corp
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Asahi Kasei Kogyo KK
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    • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
    • A61L2/0005—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor for pharmaceuticals, biologicals or living parts
    • A61L2/0011—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor for pharmaceuticals, biologicals or living parts using physical methods
    • A61L2/0017—Filtration
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    • A61L2/022—Filtration
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    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/34—Filtering material out of the blood by passing it through a membrane, i.e. hemofiltration or diafiltration
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
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    • A61M2205/00—General characteristics of the apparatus
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Definitions

  • This invention relates to a porous hollow fiber membrane and a method for the removal of a virus by using the same. More particularly, the present invention is concerned with a novel porous hollow fiber membrane which is characterized by its unique porous structure wherein the inner and outer membrane surfaces have an in-a-plane average pore diameter of 0.01 to 10 ⁇ m and the porous membrane wall has an in-a-plane porosity of not less than 10 % measured in every plane perpendicular to a radial direction of the annular cross-section of the hollow fiber membrane, said in-a-plane porosity exhibiting at least one minimum value between the inner and outer membrane surfaces.
  • the present invention is also concerned with a method for the removal of a virus from an aqueous protein solution containing a virus by the use of the abovementioned porous hollow fiber membrane.
  • the novel hollow fiber membrane and the method of the present invention are especially useful because they are extremely effective for the removal of a virus with the great advantages that both an excellent virus removal percentage and a high filtration speed can be simultaneously attained.
  • the virus removal percentage is increased but the filtration speed and the protein concentration of the filtrate are lowered. If the average pore diameter is increased, the virus removal percentage is lowered to 99% or less, which is insufficient for a membrane to be used for the removal of viruses.
  • the virus removal percentage normally required for a virus removing membrane is as high as 99.99 to 99.999999%.
  • FIG. 1 is a schematic illustration of one end portion of the porous hollow fiber membrane according to the present invention, in which numeral 1 denotes the porous polymer wall of the porous hollow fiber membrane, numeral 2 denotes a portion of a transverse cross section of the porous polymer wall, numeral 3 denotes a portion of a longitudinal cross section of the porous polymer wall and numeral 4 denotes a portion of the outer wall surface of the porous hollow fiber membrane;
  • FIG. 2 is an enlarged schematic illustration of a scanning electron photomicrograph of the portion indicated by numeral 2 in FIG. 1;
  • FIG. 4 is an enlarged schematic illustration of a scanning electron photomicrograph of the portion indicated by numeral 4 in FIG. 1;
  • FIG. 5 is a graph showing the variation of the in-a-plane porosity with the variation of the distance of the plane from the inner wall surface with respect to various types of porous hollow fiber membranes according to the present invention
  • FIG. 6 is a flow diagram illustrating one mode of the method of the present invention in which viruses are removed from an aqueous protein solution.
  • a porous hollow fiber membrane comprising a porous polymer wall having a substantially annular cross-section and a hollow space defined by the inner wall surface of said porous polymer wall which hollow space extends in the longitudinal direction of said porous polymer wall, said porous polymer wall having pores which form through-passages passing from the inner wall surface to the outer wall surface of said polymer wall, and wherein the inner and outer wall surfaces of said porous wall have an in-a-plane average pore diameter of 0.01 to 10 ⁇ m, said in-a-plane average pore diameter being an average pore diameter as measured in a plane perpendicular to a radial direction of said annular cross-section, and said porous polymer wall has an in-a-plane porosity of not less than 10% measured in every plane perpendicular to a radial direction of said annular cross-section, said in-a-plane porosity varying continuously between said inner wall surface and said outer wall surface, wherein said in-a
  • porous hollow fiber membrane of the present invention comprises a porous polymer wall having a substantially annular cross-section which membrane has a specific pore structure.
  • the porous hollow fiber membrane of the present invention has the following pore structure characteristics:
  • the in-a-plane average pore diameters in the inner and outer wall surfaces of the porous hollow fiber membrane as measured by scanning electron photomicrography are in the range of from 0.01 to 10 ⁇ m;
  • the in-a-plane porosity in each of the inner and outer wall surfaces of the porous hollow fiber membrane is at least 1.5 times the lowest value of in-a-plane porosity within the porous polymer wall.
  • in-a-plane porosity as used herein is intended to means a porosity in a plane within and on the porous polymer wall, which plane is perpendicular to a radial direction of the annular cross-section of the porous polymer wall.
  • plane has the same meaning as defined above.
  • FIGS. 1 to 4 there is shown schematic illustrations for the purpose of illustrating the specific pore structure of the porous hollow fiber membrane.
  • numeral 1 denotes the porous polymer wall of the porous hollow fiber membrane
  • numeral 2 denotes a portion of a transverse cross section of the porous polymer wall
  • numeral 3 denotes a portion of a longitudinal cross section of the porous polymer wall
  • numeral 4 denotes a portion of the outer wall surface of the porous hollow fiber membrane.
  • FIG. 2 there is shown an enlarged schematic illustration of a scanning electron photomicrograph of the portion indicated by numeral 2 in FIG. 1.
  • FIG. 3 there is shown an enlarged schematic illustration of a scanning electron photomicrograph of the portion indicated by numeral 3 in FIG. 1.
  • FIG. 4 there is shown an enlarged schematic illustration of a scanning electron photomicrograph of the portion indicated by numeral 4 in FIG. 1.
  • pores vacuum portions
  • the in-a-plane porosity varies continuously between the inner wall surface and the outer wall surface.
  • the in-a-plane porosity increases in the vicinity of each of the inner and outer wall surfaces toward a value of the in-a-plane porosity at each of the inner and outer wall surfaces, and exhibits at least one minimum value between the inner and outer wall surfaces.
  • the in-a-plane porosity at each of the inner and outer wall surfaces is at least 1.5 times the lowest value of the in-a-plane porosity within the porous polymer wall.
  • FIG. 5 there is shown a graph showing the variation of the in-a-plane porosity with the variation of the distance of the plane from the inner wall surface (hereinafter often referred to simply as "variation of the in-a-plane porosity") with respect to various types of porous hollow fiber membranes according to the present invention.
  • Curve A indicates the variation of the in-a-plane porosity with respect to a porous hollow fiber having two minimum values of the in-a-plane porosity.
  • Curve B indicates the variation of the in-a-plane porosity with respect to the porous hollow fiber of Example 1 (given later), which has one minimum value of the in-a-plane porosity at a middle portion between the inner and outer wall surfaces.
  • Curve C indicates the variation of the in-a-plane porosity with respect to a porous hollow fiber which is similar to the porous hollow fiber of Curve B in that both the hollow fibers of Curve C and Curve B have one minimum value of the in-a-plane porosity.
  • the hollow fiber of Curve C is similar to that of a Curve in the virus-removing effect because both of these hollow fibers have a minimum value of the in-a-plane porosity in a portion deviated from the middle portion to the side of the outer wall surface.
  • Porous hollow fiber membrane having various in-a-plane porosity variations can be obtained by controlling various conditions in the process of producing the porous hollow fiber membrane, that is, they can be obtained by controlling the compositions of the injection liquid and the coagulating bath, the period of time for which the spinning solution is in contact with the injection liquid and the coagulating bath and the like.
  • a preferred process for producing the porous hollow fiber is now described as follows.
  • a spinning solution of a polymer is extruded through an annular orifice to form a fiber extrudate with a hollow space while simultaneously injecting an injection liquid into the hollow space of the fiber extrudate through an injection tube provided in the center of the annular orifice.
  • the fiber extrudate should be immediately immersed into the coagulating liquid.
  • microphase separation means a state wherein a polymer-rich phase or a polymer-lean phase is stably dispersed as particles having a diameter of about 0.01 to about 5 ⁇ m in a polymer solution. Due to the formation of the particles, the polymer solution first loses its transparency, and then gradually undergoes coagulation and regeneration.
  • the resultant porous membrane has such a characteristic structure that the surface of a frozen fracture of the porous membrane consists of many particles linked together having a diameter in the range of from 0.1 to several ⁇ m (see FIGS. 2 and 3).
  • a ternary system consisting of acetone, ammonia and water in a ratio such as 35:1:50
  • an injection liquid is injected from the injection tube (e.g. 0.6 mm in diameter) at a fixed rate (e.g. 2.0 to 20 ml/min).
  • the composition and the temperature of the injection liquid are required to be controlled at least as strictly as those of the spinning solution.
  • the fiber shaped extrudate (the inner part is the injection liquid and the outer part is the spinning solution) is immediately immersed into the coagulating bath.
  • the porous hollow fiber membrane of the present invention is capable of completely removing the viruses contained in an aqueous protein solution even when the membrane has in-a-plane average pore diameters larger than the diameter of the viruses in the inner and outer wall surfaces of the membrane, due to the above-mentioned pore structure characteristics of items (1) to (4) above to the membrane.
  • the porous hollow fiber membrane of the present invention is highly effective in inhibiting the passage of viruses therethrough due to the pore characteristic change in a radial direction of the annular cross-section of the membrane wall and to the presence of a minimum value of the in-a-plane porosity at least at one portion between the inner and outer wall surfaces as mentioned in item (3) above.
  • the protein permeability and protein permeation rate of the present porous hollow fiber membrane can be improved by causing the porosity of one surface of the membrane from which a protein is permeated to become larger than that within the membrane wall.
  • V A /V W in which V A represents the permeability for an aqueous 5% by weight albumin solution and V W represents the permeability for purified water, is significantly improved when the ratio of the in-a-plane porosity in one surface of the membrane, from which permeation of the water and albumin solution is performed, to the lowest value of the in-a-plane porosities within the membrane wall, is at least 1.5, as compared with that when such ratio is 1.
  • the value of V A /V W is remarkably improved, and sometimes becomes twofold or more, when the above-mentioned ratio is at least 2.
  • the porous polymer wall have a pore structure in which the in-a-plane average pore diameter varies continuously between the inner wall surface and the outer wall surface so that from the inner wall surface toward the outer wall surface, the in-a-plane average pore diameter alternatively decreases and increases at least two times, thereby experiencing occurrences of at least a minimum value, a maximum value and a minimum value, in this order, in the continuous variation of the in-a-plane average pore diameter between the inner and outer wall surfaces, wherein the in-a-plane average pore diameter increases in the vicinity of said outer wall surface and in which the wall portion of the membrane has a layer structure as described later.
  • the in-a-plane average pore diameter increases toward a value of the in-a-plane average pore diameter at the outer wall surface.
  • the in-a-plane average pore diameter at a plane exhibiting a minimum in-a-plane porosity value with respect to the porous hollow fiber membrane of the present invention may be larger than the diameters of the viruses to be removed.
  • the membrane is capable of highly effectively inhibiting the passage of the viruses therethrough.
  • the porous hollow fiber membrane of the present invention may advantageously have a layer structure in the direction of the wall thickness, so that the membrane has the following characteristics:
  • each of such planes has a different pore diameter distribution, different average pore diameter and different in-a-plane porosity, depending on the distance, in a radial direction of the annular cross-section of the membrane wall, of the plane from the inner wall surface of the membrane.
  • the above-mentioned planes are each approximated to a section of a layer having a thickness of formula ##EQU1## wherein 2S 2 represents the diameter of fine particles formed by the microphase separation as described hereinbefore, which section is in parallel with the surface of the layer.
  • the number of layers constituting the porous polymer wall of the porous hollow fiber membrane of the present invention be in the range of from about 10 to about 300.
  • the number of layers is preferably not larger than about 300 from the viewpoint of ensuring high permeability for proteins or the like.
  • the "number of layers" as used herein is defined as ⁇ 6d/4S 2 in which d represents the wall thickness of the membrane and S 2 is as defined above.
  • a plane perpendicular to the fiber axis which plane is represented by the cross section of the porous hollow fiber membrane is approximated to a layer-form accumulation of particles having a diameter of from 0.1 to 2 ⁇ m.
  • the average shear rate of the filtrand flow on the inner wall surface of the hollow fiber be increased.
  • the shear rate is 1000 sec -1 or more
  • the capability of inhibiting the passage of viruses is about 10 times that exhibited when it is 0.
  • the upper limit of the in-a-plane porosity with respect to the porous hollow fiber according to the present invention is not limited but may preferably be about 80% from the viewpoint of ease of production of the membrane.
  • the hollow fiber membrane of the present invention preferably has a wall thickness of from 10 ⁇ m to 200 ⁇ m. If a membrane having a wall thickness of less than 10 ⁇ m is employed, the virus removal percentage is lowered. On the other hand, if a membrane having a wall thickness of more than 200 ⁇ m is employed, the protein permeability decreases, leading to a lowering of the recovery of protein.
  • the number of pores which are present in each of the porous inner and outer surfaces of the polymer wall of the porous hollow fiber membrane of the present invention is preferably 10 6 /cm 2 or more.
  • the apparent average pore diameter in the porous polymer wall is in the range of 14 to 150 nm.
  • a membrane made of a hydrophilic polymer has a large value of V A /V W in which V A and V W are as defined above and, hence, preferable.
  • a porous hollow fiber membrane produced by a microphase separation method has a higher filtration rate and a higher filtration capacity than porous hollow fiber membranes produced by other methods such as a method in which a substance having a low molecular weight is emulsified and mixed with a polymer solution to obtain a spinning solution, the obtained solution is spun into a hollow fiber and then the substance having a low molecular weight is removed from the hollow fiber. Therefore, a porous hollow fiber membrane produced from a hydrophilic polymer by a microphase separation method is preferably used for removing viruses from an aqueous protein solution having a high protein concentration.
  • Blood plasma is an example of an aqueous protein solution which may be subjected to the removal of viruses according to the method of the present invention.
  • the chemical structure of the polymer constituting the porous hollow fiber membrane has a large effect on the performance of the membrane.
  • a membrane made of a polymer containing a large number of hydroxy groups, such as a regenerated cellulose is preferable from the viewpoints of the filtration capacity of the membrane and the recovery of proteins.
  • a membrane produced from a cuprammonium regenerated cellulose by a microphase separation method is especially preferable.
  • Viruses in human blood plasma for example, hepatitis virus, AIDS (acquired immune deficiency syndrome) virus, etc., are generally highly infectious to human beings and have a serious effect on human bodies after infection. Therefore, in the removal of these viruses from human blood plasma, the removal percentage is required to be 99.999% to 99.999999%.
  • a porous hollow fiber membrane for removing viruses with such a high removal percentage, wherein the membrane has a layer structure consisting of 10 or more layers and the ratio of the minimum value of the in-a-plane porosity (%) to the value of the wall thickness ( ⁇ m) is in the range of from 0.05 to 2.0.
  • a membrane having a layer structure consisting of 100 or more layers is more preferable.
  • a method for the removal of a virus contained in an aqueous protein solution which comprises contacting an aqueous protein solution containing a virus with a porous hollow fiber membrane comprising a porous polymer wall having a substantially annular cross-section and a hollow space defined by the inner wall surface of said porous polymer wall which hollow space extends in the longitudinal direction of said porous polymer wall, said porous polymer wall having pores which form through-passages passing from the inner wall surface to the outer wall surface of said polymer wall, and wherein the inner and outer wall surfaces of said porous polymer wall have an in-a-plane average pore diameter of 0.01 to 10 ⁇ m, said in-a-plane average pore diameter being an average pore diameter as measured in a plane perpendicular to a radial direction of said annular cross-section, and said porous polymer wall has an in-a-plane porosity of not less than 10% measured in every plane perpendicular to a radial
  • the method of the present invention can be suitably applied to a virus-containing aqueous protein solution such as plasma, particularly human plasma, or the like.
  • the aqueous protein solution to be treated by the method of the present invention has a protein concentration of 0.5 to 30% by weight in terms of total protein concentration which protein is part of useful components of the solution.
  • aqueous protein solutions there may be mentioned human or animal blood or plasma, materials and intermediates for plasma derivatives, aqueous solutions containing plasma derivatives, growth hormone, injections containing physiologically active substances such as growth hormone, vaccine and the like, cell culture fluid, aqueous product solutions in the fermentation industry and intermediates therefor, diagnostics, serums for cell culturing, vaccine and the like.
  • viruses to be removed by the method of the present invention there may be mentioned hepatitis virus, AIDS virus, influenza virus, poliomyelitis virus and the like which are pathogenic to human beings and/or animal.
  • an aqueous protein solution containing a virus is contacted with either the inner wall surface or the outer wall surface of the porous hollow fiber membrane.
  • the contact of the aqueous protein solution with the wall surface of the porous hollow fiber membrane may be effected either by flowing the solution along the wall surface or by applying the solution in the stationary state onto the wall surface.
  • a trans-membrane pressure of about 0.1 to 1 atm is applied.
  • the virus is effectively captured in the porous hollow fiber membrane and, thus, can be removed from the aqueous protein solution, not only with an extremely high virus removal percentage but also with a high protein permeability. Therefore, the high filtration speed is realized. Further, it should be noted that according to the method of the present invention, the protein contained in the aqueous protein solution is not denatured and there is no danger that the biological activity of the protein is lowered.
  • FIG. 6 there is a flow diagram illustrating one mode of the present invention in which viruses are removed from an aqueous protein.
  • a plurality (about 10,000) of the porous hollow fiber membranes of the present invention are bundled to obtain a module.
  • Two modules are designated by F 1 and F 2 .
  • Plasma obtained from a plurality of persons is pooled in a tank T 1 .
  • the temperature of the plasma is maintained at about 4° C.
  • the plasma is supplied to the module F 1 or F 2 through a line L 1 by the manipulation of switches S 4 S 5 and S 1 at a predetermined flow rate by a pump P 1 (in this case, the plasma is flowed into the hollow space of the hollow fiber membrane).
  • the amount of the pressure applied to the module F 1 or F 2 is given as the difference between the pressure values at an entry port side pressure gage G 1 and an outlet side pressure gage G 2 and a vacuum line.
  • the switch S 1 By manipulating the switch S 1 , the module F 1 or F 2 is selected.
  • a filtrate from the modulate F 1 or F 2 flows to a tank T 2 through a line L 4 by the manipulation of a switch S 3 . Any residual filtrand flows through a line L 2 , and, by the manipulation of the switch S 4 is then supplied to the module F 1 or F 2 again by the pump P 1 .
  • the module F 1 or F 2 is back washed by a buffer solution stored in a tank T 3 .
  • the initial part of the liquid flowing back into the hollow space of the hollow fiber membranes by the back-washing enters the line L 2 , and the latter part of the liquid is led out of the system through a line L 5 by the manipulation of switches S 1 and S 5 .
  • switches S 1 and S 5 By this procedure, not only the back-washing of the hollow fibers is conducted, but also an excessive increase in the protein concentration within the line L 2 is prevented, thereby enabling the filtration speed in the module F 1 and F 2 to be stably maintained, so that the recovery of a virus-free protein solution can be attained with high efficiency.
  • the present invention can be advantageously utilized in fields such as medicine, biochemistry, animal husbandry and the like.
  • the in-a-plane average pore diameter, the in-a-plane porosity, the bulk porosity and the apparent average pore diameter were measured by the following methods.
  • N(r) is determined by, for example, the method of stereology [see, for example, Norio Suwa, “Teiryo Keitaigaku (Quantitative morphology)” (published by Iwanami Shoten, Japan), p. 185-272].
  • the in-a-plane porosity (Pre) with respect to a plane in the polymer wall of the hollow fiber is obtained by calculation from the following formula ##EQU4## wherein r and N(r) are as defined above.
  • the pore radius distribution [N(r)] is determined in the same manner as mentioned above.
  • Ri, Ro, l and W respectively represent the inner diameter (cm), outer diameter (cm), length (cm) and weight (g) of the hollow fiber after drying in vacuo;
  • ⁇ is the density of the polymer constituting the porous hollow fiber.
  • d is the wall thickness (cm) of the porous hollow fiber membrane
  • ⁇ is the viscosity coefficient (centipoise)
  • P rp is the bulk porosity of the porous hollow fiber membrane (%)
  • J and ⁇ P are as defined above.
  • Cellulose linter having a viscosity average molecular weight of 1.5 ⁇ 10 5 was prepared according to a customary known method.
  • the prepared cellulose linter was dissolved in an aqueous cuprammonium solution having ammonia and copper concentrations of 6.8% by weight and 3.1% by weight, respectively, so that the final concentration of the cellulose linter in the resulting cellulose linter solution became 7.0 5 by weight.
  • the cellulose linter solution was filtered, followed by degassing, thereby to obtain a spinning solution.
  • the spinning solution was extruded through a spinneret having an orifice diameter of 2 mm, an injection-tube outside diameter of 0.8 mm and an injection-tube inside diameter of 0.6 mm at a delivery rate of 2.0 ml/min to form a fiber extrudate with a bore, while simultaneously injecting an injection liquid through the injection tube disposed in the center of th orifice into the bore at a delivery rate of 5.0 ml/min.
  • both the spinning solution and injection liquid were maintained at 25° ⁇ 0.1° C.
  • As the injection liquid a solution whose composition was strictly controlled so that the proportions of water, acetone and ammonia were 100.0:70.0:1.0 by weight was employed.
  • the fiber extrudate was immediately introduced into a coagulating bath maintained at a temperature of 25° ⁇ 0.1° C. whose composition was strictly controlled so that the proportions of water, acetone and ammonia were 100.0:70.0:1.0 by weight, followed by reeling up at a velocity of 7.0 m/min from the bath.
  • the fiber extrudate which had been transparent, blue upon extrusion thereof gradually became white showing occurrence of a microphase separation, followed by coagulation thereby enabling the extrudate to solidify in a hollow fiber form.
  • the fiber was regenerated in a 2% by weight aqueous sulfuric acid at 20° ⁇ 0.1° C. and subsequently washed with water, followed by drying.
  • the resulting hollow fiber had an annular cross-section, and had an outside diameter of 305 ⁇ m, a wall thickness (d) of 30 ⁇ m and an inside diameter of 245 ⁇ m.
  • the in-a-plane porosity (Pre) in every plane perpendicular to a radial direction of the annular cross-section of the hollow fiber was measured and plotted against the value of the distance of the plane from the inner wall surface divided by the wall thickness of the hollow fiber to obtain Curve B of FIG. 5.
  • the minimum value of Pre in this case, it was also the lowest value was 23%, while the Pre's in the inner and outer wall surfaces of the hollow fiber were both about 60%.
  • the hollow fiber of the present invention had an average particle diameter (2S 2 ) of 0.50 ⁇ m. Further, as a result of the observation of planes parallel to the membrane surfaces of the hollow fiber by means of a scanning detection microscope it was confirmed that the hollow fiber of the present invention had a layer structure.
  • D 3 was 0.15 ⁇ m
  • D 3 /D 2 2as 1.32 and D 3 /D 4 was 1.31.
  • the bulk porosity of the hollow fiber was 48.1%.
  • the apparent average pore diameter (2r f ) was 50 nm.
  • a filtration test was conducted using as a model substance of a virus a 5% by weight aqueous albumin solution containing colloidal silica particles (Cataloid® S180P manufactured and sold by Catalysts and Chemicals Industries Company limited, Japan) having a particle size of 70 to 90 nm. The filtration test was carried out at 31° C. by flowing the aqueous albumin solution in the hollow fiber at a transmembrane pressure of 200 mmHg.
  • Table 1 The results obtained are shown in Table 1. Further, the filtrate was sprayed over a mesh for electron microscope which was coated with carbon, and then the existence of particles on the mesh was examined by means of an electron microscope. As a result, complete removal of the colloidal silica particles was confirmed.
  • the permeability of albumin was about 98% as measured by liquid chromatography.
  • Cellulose linter having a viscosity average molecular weight of 2.00 ⁇ 10 5 was dissolved in the same cuprammonium solution as employed in Example 1 so that the concentration of the cellulose linter in the resulting cellulose linter solution became 8.0% by weight.
  • the cellulose linter solution was filtered, followed by degassing, thereby to obtain a spinning solution. From this spinning solution, a regenerated cellulose porous hollow fiber membrane was obtained under substantially the same conditions as in Example 1.
  • the porous polymer wall of the hollow fiber had substantially the same pore structure as described in Example 1.
  • a filtration test was conducted in substantially the same manner as in Example 1, except that use was made of colloidal silica particles (Cataloid® ST45P manufactured and sold by Catalists and Chemicals Industries Company Limited, Japan) having a particle diameter of 35-55 nm.
  • the results of the filtration test are shown in Table 1.
  • the albumin permeability as measured by liquid chromatography was about 98%.
  • a virus removal test was conducted with respect to the plasma derived from hepatitis B virus positive blood which plasma had a total protein concentration of 5.9% and a relative concentration of hepatitis B virus in terms of DNA of 1000 units. That is, the plasma was subjected to perpendicular filtration in which the plasma was fed into the hollow fiber at its one end, while the other end of the hollow fiber was closed, at a trans-membrane pressure of 100 mmHg. The filtration rate was 0.030 l/m 2 hr mmHg.
  • the relative concentration of the hepatitis B virus in the filtrate in terms of DNA was evaluated by the hybridization method using an isotope-labeled cDNA coding for hepatitis B virus.
  • the relative concentration was below the detection limit value, thereby enabling complete removal of the virus from the plasma to be confirmed.
  • the permeability of the total proteins as measured by liquid chromatography was 90%.
  • a cellulose diacetate having a degree of acetylation of 54.2% and a polymerization degree of 190 was dissolved in a mixed solvent comprised of acetone and methanol in a weight ratio of 5/1 containing CaCl 2 2H 2 O and cyclohexanol, thereby to obtain a spinning solution.
  • a mixed solvent comprised of acetone and methanol in a weight ratio of 5/1 containing CaCl 2 2H 2 O and cyclohexanol, thereby to obtain a spinning solution.
  • a hollow fiber was spun.
  • the in-a-plane porosities in the inner and outer wall surfaces of the hollow fiber were 28% and 15%, respectively, and the in-a-plane porosities within the wall of the hollow fiber were 20% or more.

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EP0302949B1 (en) 1992-06-03
ATE76779T1 (de) 1992-06-15
US4816072A (en) 1989-03-28
EP0302972A1 (en) 1989-02-15
JPH0450054B2 (enrdf_load_stackoverflow) 1992-08-13
ZA875900B (en) 1988-02-12
EP0317676A1 (en) 1989-05-31
JPH01148305A (ja) 1989-06-09
EP0302949A1 (en) 1989-02-15

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